Why turbo a Jeep, and How?

[Kuhn]

This thread is just a bunch of ideas/info that I have, and I'm looking for any and all info... So here it is:

I've been annoyed for a long time with the performance of the 4.0L with 35's and 3.73 gears. Shortly I'm throwing a Ford 8.8 axle in the rear with a locker and 4.11 gears (unless somebody has a good argument for 4.88 gears).

But even with this gearing change I'm sure running at highway speeds will still be done from the right lane. I think a turbo is an answer to this problem. A smaller turbo might even spool soon enough to help off-road... Especially a ceramic blade, double ball-bearing turbo off of an R32 Skyline, with a 4'' exhaust dump! I've heard that I could safely run that sized turbo at 6.5 psi without an intercooler, but an MSD Boost Timing Master would have to be used to reduce timing 1.5 degrees for each psi (to avoid knocking). Adding an intercooler beneath the hood vent and adding a scoop on that vent would allow for about one more psi. And an alcohol/water injection kit could be hooked up to a boost pressure switch (spraying after 6psi or so) and used to spray after the intercooler and onto the intercooler itself... I would imagine this would alow for atleast 1psi more... That's a total of 8 - 8.5 psi on this turbo, which would be fully spooled by 1500 - 1800rpm! ...This would be enough to nearly double hp and ft.lbs.

Here's a list of everythig needed:
The Basics
-Small Ball-Bearing turbo ($400 used)
-MSD Ignition - PN# 6200 ($180)
-Walbro 255 Fuel Pump ($100)
*Stock injectors will help atomize the fuel for efficiency
-Guages: Air/Fuel, Boost, EGT, Pyro for Trans Temp ($$ Varies)
-Fuel Management Unit - I'm still looking for the best one
-Electronic Exhaust Cutout - optional ($200)
-MSD Boost Timing Master ($200)
-Thicker head gasket to lower compression ($100)
-Blow Off Valve (Varies)
-Boost Controller (Varies)
-Custom tubing and bracketry
For Some Extra Fun
-Top Mount Intercooler (Varies)
-Hood Scoop ($30)
-Water/Alcohol Injection ($200)

Any and all input will be appreciated. And I will update this over the next couple months since we all know that 1 demonstration is better than 1000 expert oppinions.

[fredjacksonsan]

Yes, why turbo a Jeep?

Just replace the engine

[Kuhn]

Thank you for your input. I want to turbo because it is the most efficient form of forced induction that does not include nitrous. The way I want to do it will actually provide more torque than the avenger supercharger kit that's been floating around. Also... It's so much cheaper than an engine swap (mpg and parts)... since I never go half way. (Viper engine or nothing! ) A turbo kit could also be adapted to that Viper engine!
Did you do an engine swap? If so, I would really like to know more.

[Kuhn]

I just noticed that you're a Moderator. No offense, but do you own a Jeep Wrangler? It's slow on the expressway! I ran with that idea and adapted this turbo idea to provide as much low end torque as possible. Thanks again.

[Ray H]

Your power problem is the tire size and weight, plain and simple. The best thing you can do to offset the tire size is to gear it appropriately. For 35s, that would mean minimum 4.56s, more likely 4.88s.
The issue with tire weight cant really be completely overcome. Even with a turbo or Viper engine, you are still trying to spin alot of weight thats a long distance from the center of the hub. How much more do four 35s weigh compared to the four 29s that came on the Jeep? Answer: ALOT.
It doesnt matter how much money you throw at the Jeep (within reason), it will never be quick with 35s on it. The best thing you can do to keep it cruising on the interstate is proper gearing.
Honestly, if you wanted a Jeep that will cruise the interstates in the left lane and pass everyone going up hill, youve ruined that by putting 35s on it.
I mean come on, youve got a ricer, youve got to know how important light weight wheels and tires are and a low center of gravity.

[Kuhn]

I'm definately changing gearing first. But would 70-75mph be difficult with 4.88 gearing? I will have to calculate what rpms I'll be doing at that speed with 4.88.
Oh yeah, each tire and wheel weigh nearly 100lbs. That's 400lbs of rotating mass and 100 more just sitting on the back. That's a huge problem, but nobody can tell me that a turbo can't compensate for that power loss. It looks like I'm just going to have to do it once I get all the parts together and let everybody know how it goes.

[fredjacksonsan]

Originally Posted by Kuhn

I just noticed that you're a Moderator. No offense, but do you own a Jeep Wrangler? It's slow on the expressway! I ran with that idea and adapted this turbo idea to provide as much low end torque as possible. Thanks again.

None taken. Yep, we have owned several Wranglers. The best solution to larger tires really is to change the gearing, as Ray has mentioned.

With big tires, if you simply increase the power of the engine, then the transmission or other drivetrain parts are most likely to fail. If you fix the gearing first, then the trans (and engine) will not have to work as hard to drive those big wheels/tires.

[Kuhn]

Originally Posted by fredjacksonsan

The best solution to larger tires really is to change the gearing, as Ray has mentioned.

I am installing a Ford 8.8 soon, so I will change the gearing then (in both axle obviously). I have calculated that I'd be doing about 2500rpms on the expressway with 4.88 gears... which may be expensive, but infrequent. And if I am calculating ths correctly (since I think I actually have 3.05 gears) I should accelereate about 60% faster than I do now. And a locker will ensure that whatever happens... It gets to the ground. I'm starting with that, but I have most of the parts needed for the turbo, so I think that may get used this summer.